Stents are generally cylindrically-shaped devices that function to hold open and sometimes expand a segment of a blood vessel or other lumen such as a coronary artery. They are particularly suitable for use to support the lumen or hold back a dissected arterial lining which can occlude the fluid passageway therethrough. A stent is introduced into a patient's vasculature and advanced to the deployment site in a collapsed state. Once in position, the stent is allowed to expand so as to engage the vessel walls.
In order to facilitate the stent's introduction into a patient's vasculature and its advancement therethrough, it is desirable for the stent to have as minimal a profile as possible while in its collapsed state. Conversely, the stent should preferably provide as much coverage of the vessel walls as possible while in its expanded state. These seemingly conflicting design parameters have heretofore been addressed with the use of stent patterns that represent trade-offs. Accordingly, some stent patterns serve to minimize cross-section of the stent in its collapsed state while others serve to maximize coverage of the stent while in its expanded state. A stent configuration is needed that provides for a greater spread between its profile while in the collapsed condition and its coverage in the expanded condition than has heretofore been possible.
Some stents are designed to be self expanding and open without a balloon catheter. In these cases, the stent is enclosed in a sheath on the catheter and positioned inside the patient's vascular. The sheath can be retracted when the catheter end is at the designated location, pushing the stent out to expand upon release from the sheath. In this situation, the size of the sheath that covers the stent in its collapsed state is an important factor in the overall profile of the working portion of the device. The inner diameter of the sheath is limited by the diameter of the self-expanding stent in its collapsed state. For many current stent designs, the collapsed diameter is defined by the width of a crown multiplied by the number of crowns, divided by π. If the diameter of the stent could be reduced in the collapsed state, a smaller sheath diameter could be employed reducing the overall profile of the device.